Ultraviolet radiation water treatment system

ABSTRACT

A water treatment system that performs a water purifying treatment by use of ultraviolet radiation, comprises a front stage ultraviolet radiation device for radiating ultraviolet light in a front stage process in a water purifying treatment process, a rear stage ultraviolet radiation device for radiating ultraviolet light in a rear stage process, and a controller for controlling these ultraviolet radiation devices.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromprior Japanese Patent Applications No. 2005-095943, filed Mar. 29, 2005;and No. 2005-346147, filed Nov. 30, 2005, the entire contents of both ofwhich are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an ultraviolet radiation watertreatment system for performing a water purifying treatment by use ofultraviolet radiation.

2. Description of the Related Art

Conventionally, water treatment systems represented by water systemshave been operated on the basis of ensuring hygiene by chlorinesterilization.

However, in recent years, there have occurred water system contaminationaccidents caused by emerging or reemerging pathogenic microbes such ascryptosporidium, giargia and the like.

Further, the mass generation of algae through eutrophication of lakes,dams, and rivers as water system water sources, and increasing pollutionby organic matters and the like has caused abnormal odor and taste,coloring disorders, aggregation and deposition inhibition, filtrationblockage, leakage into filtered water, and other problems.

Furthermore, there has occurred a problem where chlorine agents to beinjected into water for sterilization react with organic matters in rawwater, thereby generating harmful by-products such as trihalomethanes(It is the general term showing the total amount of Chloroform,Bromoform, Bromodichloromethane, and Dichlorochloromethane.).

These problems have come to a level not to be controlled by a prior-artwater treatment system of the basic treatment process includingaggregation and deposition, filtration, and chlorine treatment.

In such circumstances, a sterilization (disinfection) technology by anultraviolet radiation treatment (hereinafter referred to also asultraviolet disinfection) has attracted much attention as an alternativesterilization technology to the conventional chlorine sterilization. Theultraviolet disinfection has an advantage that it does not requirecomplicated procedures of chemical injection, and does not generateharmful by-products. For this reason, in water treatment plants and thelike, the ultraviolet radiation treatment is adopted in some cases forthe purpose of sterilization and oxidation of residual organic matters.However, from the viewpoint of the transmittance efficiency ofultraviolet light, a treatment where ultraviolet light is radiated tofiltered water or aggregated or deposited water is carried out ingeneral.

On the other hand, in some cases, ultraviolet radiation is applied toraw water for the purpose of aggregation improvements, elimination ofinfectiousness of pathogenic microbes such as criptosporidium, and thelike. This is a treatment where ultraviolet light is radiated in theplace of performing a chlorine sterilization to raw water. As mentionedpreviously, unlike the chlorine treatment, this treatment does notgenerate by-products such as trihalomethanes even if ultraviolet lightis radiated. Further, ultraviolet light is highly efficient to damagethe reproductive power of criptosporidium and eliminate itsinfectiousness. Therefore, the ultraviolet radiation treatment isemployed.

In the water purifying treatment, it is preferable that the reproductionof algae included in raw water is prevented, and it has been confirmedthat the ultraviolet radiation treatment is also effective as atreatment to prevent the reproduction of algae.

Meanwhile, the radiation efficiency of ultraviolet light changes withthe turbidity and chromaticity of water to be treated. Especially, it isdifficult to control the water quality of raw water. Therefore, it isdifficult to appropriately maintain the radiation efficiency in theultraviolet radiation treatment, which has been a problem in the priorart.

In order to solve such a problem, there is proposed a technology forrealizing an appropriate ultraviolet radiation control by detecting aturbidity of raw water, and controlling a flow rate of raw water that ismade to flow through a water pipe containing an ultraviolet lampaccording to the detected turbidity (refer to, for example, Jpn. Pat.Appln. KOKAI Publication No. 5-169059). In this document, it is proposedto use ultraviolet radiation in an algicidal treatment of water planktonin water storage basins and the like.

Further, there is also proposed a technology for realizing anappropriate ultraviolet radiation control by use of a particle meter inthe place of a turbidity meter (refer to, for example, Shigeo Kimura et.al., “Investigation on Basic Performance Evaluation of ParticleMeasuring Devices”, Water System Association Magazine, vol. 71, No. 10,pp. 31 to 51, October, 2002). Furthermore, there is proposed anultraviolet radiation system that controls an output of an ultravioletlamp by use of a turbidity meter and a particle meter in a system forradiating ultraviolet light into raw water in a water purifyingtreatment plant (refer to, for example, Jpn. Pat. Appln. KOKAIPublication No. 2004-188273).

In the ultraviolet radiation system and the ultraviolet radiationtreatment method described in the above-described prior-art documents,there are problems as shown below.

In general, algae that cause problems in aggregation and depositioncannot be countermeasured only by radiating ultraviolet light intotreated water after the aggregation and deposition treatment of rawwater. Thus, in order to use the ultraviolet radiation effect as acountermeasure against algae, it is necessary to radiate ultravioletlight into raw water before the aggregation treatment.

However, the water quality of raw water changes greatly with watersources, fluctuations in meteorological phenomena, and the like. Morespecifically, the turbidity, the number of microbes, and theconcentration of organic matter in raw water change greatly owing to themass reproduction of algae and rainfalls, and in normal cases, theultraviolet transmittance decreases as these values increase. As aresult, the effect of the ultraviolet radiation cannot be attainedsufficiently, and the effects of not only the algae countermeasures, butalso the sterilization (disinfection) treatment of pathogens and thelike decrease, which is another problem with the prior art.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provideda water treatment system for performing a water purifying treatment byuse of ultraviolet radiation, comprising:

a first ultraviolet radiation device which radiates ultraviolet in a rawwater coagulation/sedimentation treatment process as a front stageprocess of a water purifying treatment process;

a second ultraviolet radiation device to radiate ultraviolet totreatment water at the front stage process in a rear stage process ofthe water purifying treatment process; and

a controller which controls the first and second ultraviolet radiationdevices.

Additional advantages of the invention will be set forth in thedescription which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. Theadvantages of the invention may be realized and obtained by means of theinstrumentalities and combinations particularly pointed out hereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention, andtogether with the general description given above and the detaileddescription of the embodiments given below, serve to explain theprinciples of the invention.

FIG. 1 is a block diagram showing major portions of a water treatmentsystem according to a first embodiment of the invention;

FIG. 2 is a block diagram showing major portions of a water treatmentsystem according to a second embodiment of the invention;

FIG. 3 is a graph showing the relation between the turbidity and theultraviolet transmittance according to the second embodiment;

FIG. 4 is a graph showing the relation between the fluorescenceintensity and the ultraviolet absorbance according to the secondembodiment;

FIG. 5 is a graph showing the relation between the fluorescenceintensity and the carbon concentration of dissolved organic mattersaccording to the second embodiment;

FIG. 6 is a block diagram showing major portions of a water treatmentsystem according to a third embodiment of the invention;

FIG. 7 is a diagram showing an internal configuration of a front stageultraviolet radiation device according to the third embodiment;

FIG. 8 is a schematic diagram showing a water treatment system accordingto a fourth embodiment of the invention and a water purifying plant towhich the water treatment system is applied;

FIG. 9 is a block diagram showing a schematic configuration of amonitoring control unit 62 assembled in the water treatment systemaccording to the fourth embodiment;

FIG. 10 shows recorded contents of an injection and radiation controlpattern table 71 according to the fourth embodiment;

FIG. 11 is a view showing a display screen 83 of a display unit 72according to the fourth embodiment;

FIG. 12 is a block diagram showing a schematic configuration of a frontstage injection and radiation control unit in the water treatment systemaccording to the fourth embodiment;

FIG. 13A is a graph showing the relation between the turbidity andsodium hypochlorite in the water treatment system according to thefourth embodiment;

FIG. 13B is a graph showing the relation between the turbidity and theultraviolet injection and radiation amount in the water treatment systemaccording to the fourth embodiment; and

FIG. 13C is a graph showing the relation between the number of UV lampsand the designated radiation amount in the water treatment systemaccording to the fourth embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be illustrated in more detailswith reference to the accompanying drawings hereinafter.

First Embodiment

FIG. 1 is a block diagram showing major portions of a water treatmentsystem according to a first embodiment of the present invention.

The system has a sand basin 1 to which raw water pumped up through anintake (not shown) is guided through a water conduit pipe, and a waterbasin 2 which temporarily stores the raw water which is supplied fromthe sand basin 1. An amount of the raw water to be supplied to a waterpurifying process is adjusted by the water basin 2.

The system also has a coagulation/sedimentation basin 3 to guide the rawwater supplied from the water basin 2 via a front stage treatmentprocess. In the front stage treatment process, a raw water flow meter 4and a first ultraviolet radiation device (hereinafter, referred to alsoas front stage ultraviolet radiation device) 5 are arranged on the wayof pipes for supplying the raw water from the water basin 2 to thecoagulation/sedimentation basin 3. Further, a bypass piping 6 isarranged for the raw water to take a roundabout route away from thefront stage ultraviolet radiation device 5.

The bypass piping 6 is connected to the inlet side of the front stageultraviolet radiation device 5 via an inlet three-way valve 7 a, and isconnected to the outlet side thereof via an outlet three-way valve 7 b.The inlet three-way valve 7 a and the outlet three-way valve 7 b arevalves for changing routes of the raw water, respectively. On the way ofthe piping, the water to which ultraviolet has been radiated by thefront stage ultraviolet radiation device 5 is supplied to thecoagulation/sedimentation basin 3.

In the coagulation/sedimentation basin 3, an aggregating agent isinjected, and turbidity matters in the raw water are removed in theprocedures of high speed stirring, low speed stirring, and deposition.More specifically, fine sands and dirts, and colloidal organic mattersget together to form flocks, and turbidity matters are deposited andremoved. At this moment, part of algae and pathogenic microbes dead orstill alive after the ultraviolet radiation by the front stageultraviolet radiation device 5 are also taken in flocks and removed.

Further, in this system, a sedimented water flow meter 9 and a secondultraviolet radiation device (hereinafter, referred to also as rearstage ultraviolet radiation device) 10 are arranged on the way of thepiping for supplying treatment water from the coagulation/sedimentationbasin 3 to a filter basin 8 in a rear stage treatment process as well.In addition, a bypass pipe 11 is arranged for the treatment water totake a roundabout route away from the rear stage ultraviolet radiationdevice 10.

The bypass pipe 11 is connected to the inlet side of the rear stageultraviolet radiation device 10 via an inlet three-way valve 12 a, andis connected to the outlet side thereof via an outlet three-way valve 12b. The inlet three-way valve 12 a and the outlet three-way valve 12 bare valves for changing routes of the raw water, respectively. On theway of the piping, the treatment water to which ultraviolet has beenradiated by the front stage ultraviolet radiation device 5 is suppliedto the filter basin 8.

In each inside of the front stage ultraviolet radiation device 5 and therear stage ultraviolet radiation device 10, a plurality of ultravioletlamps for radiating ultraviolet are arranged. Each of the ultravioletlamps is supplied with electric power from ultraviolet lamp powersources 13 a, 13 b, and is lit.

A water purifying treatment monitor control device (hereinafter referredto as controller) 14 of the system is connected to the ultraviolet lamppower sources 13 a, 13 b via a control signal line, and controls theoutput of each of the ultraviolet lamp power sources 13 a, 13 b.Thereby, the amount of electric power supplied to each of theultraviolet lamps of the ultraviolet radiation devices 5, 10 isadjusted.

To the controller 14, a measurement value of a raw water flow rate isinput from the raw water flow meter 4, and a measurement value of asedimented water flow rate is input from the sedimented water flow meter9. Also, to the controller 14, an ultraviolet transmittance of the rawwater measured by a raw water ultraviolet transmissometer 16 is input,and an ultraviolet transmittance of the sedimented water measured by asedimented water ultraviolet transmissometer 18 is input.

The raw water ultraviolet transmissometer 16 is connected to a raw watersampling pipe 15, and measures an ultraviolet transmittance of a rawwater sample taken up by the raw water sampling pipe 15 from a pipingfor connecting the water basin 2 and the front stage ultravioletradiation device 5. On the other hand, the sedimented water ultraviolettransmissometer 18 is connected to a sedimented water sampling pipe 17,and measures an ultraviolet transmittance of a sedimented water sampletaken up by the sedimented water sampling pipe 17 from a piping forconnecting the coagulation/sedimentation basin 3 and the rear stageultraviolet radiation device 10.

Moreover, ultraviolet illuminance meters 19, 20 for sensing theilluminance of an arbitrary point in the inside are arranged,respectively, to the front stage ultraviolet radiation device 5 and therear stage ultraviolet radiation device 10. Measurement values fromthese ultraviolet illuminance meters 19, 20 are input to the controller14.

(Operation and Effects of First Embodiment)

Hereinafter, the operation and effects of the present embodiment will beexplained.

The controller 14 calculates the respective ultraviolet illuminances inthe insides of the front stage ultraviolet radiation device 5 and therear stage ultraviolet radiation device 10 by use of the followingequation (1). Herein, the ultraviolet illuminance is maximum at thesurface of the ultraviolet lamp, and decreases gradually away from thelamp. The decrease amount at this moment is calculated with anultraviolet transmittance to a fluid to be treated (raw water orsedimented water) flowing in the piping, and a distance from the lampsurface:

$\begin{matrix}{{I = {\left( \frac{U_{V}}{4\;\pi\; Z_{0}^{2}} \right) \times {\exp\left( {{\ln\left( {T/100} \right)} \times Z} \right)}}}\left( {{mW}/{cm}^{2}} \right)} & (1)\end{matrix}$

where I means an ultraviolet illuminance (mW/cm²); U_(v) means anultraviolet output of the lamp (mW); T means an ultraviolettransmittance (%), Z₀ means a distance from the lamp (cm); and Z means adistance in which ultraviolet penetrates the raw water or the treatmentwater (cm).

Meanwhile, measurement values of the ultraviolet transmittance are inputto the controller 14 from the raw water ultraviolet transmissometer 16and the sedimented water ultraviolet transmissometer 18.

The performance of algicidal treatment and sterilization (disinfection)by ultraviolet radiation with the front stage ultraviolet radiationdevice 5 and the rear stage ultraviolet radiation device 10 isdetermined by an ultraviolet amount based on an illuminance thatmicrobes included in the raw water or the treatment water flowing in thepiping receive, and time. In general, the ultraviolet amount is definedby the following equation (2):Dose=I×t(mJ/cm²)  (2)

where Dose means an ultraviolet amount (mJ/cm²); I means an ultravioletilluminance (mW/cm²), and t means a radiation time (s).

Further, an ultraviolet amount necessary to deaden microbes to betreated or inactivate the same (destroy the reproductive power, ordestroy the infectious power in the case of pathogenic microbes) differsgenerally depending on the kinds of microbes. Accordingly, it isnecessary to take into consideration the performances of the ultravioletradiation devices 5, 10 according to the kinds of microbes to betreated.

(Control of Front Stage Ultraviolet Radiation Device 5)

In the present embodiment, the front stage ultraviolet radiation device5 is arranged in the front stage of the coagulation/sedimentation basin3. Therefore, it is effective as countermeasures against not merelypathogenic microbes living in the raw water but also algae. Accordingly,the controller 14 controls the output of the ultraviolet lamps of thefront stage ultraviolet radiation device 5 in order to attain theradiation of the ultraviolet amount necessary to deaden or inactivate aplurality of pathogenic microbes and algae.

The controller 14 controls the output of the ultraviolet lamps of thefront stage ultraviolet radiation device 5 in consideration of themeasurement value by the raw water ultraviolet transmissometer 16, themeasurement value by the raw water flow meter 4, the arrangement of theultraviolet lamps in the front stage ultraviolet radiation device 5, andthe raw water flowing condition that changes depending on the internalstructure and the flow rate, by use of the arithmetic equations such asthe above arithmetic equations (1) to (2). More specifically, thecontroller 14 calculates a necessary ultraviolet output value accordingto the ultraviolet transmittance and the flow rate change by thearithmetic equations. Thereby, the controller controls the electricpower to be supplied from the ultraviolet lamp power source 13 a to theultraviolet lamps in the front stage ultraviolet radiation device 5.

Further, when the controller 14 determines that the ultraviolettransmittance of the raw water is sufficiently high in comparison with areference value on the basis of the measurement value from the raw waterultraviolet transmissometer 16, the controller makes a control todecrease the output of the ultraviolet lamps of the rear stageultraviolet radiation device 10 to the lower limit value, or stop theoperation.

Namely, when the ultraviolet transmittance of the raw water is high, itis possible to attain the sufficient algicidal treatment andsterilization (disinfection) performance even with only the front stageultraviolet radiation device 5. Accordingly, by decreasing theperformance of the rear stage ultraviolet radiation device 10, it ispossible to save the electricity consumption. In this case, from theviewpoint of the characteristics of the ultraviolet lamp, a constantwait time is required for the ultraviolet lamp to be lit and perform itsultraviolet output stably. For this reason, the output decreaseoperation is preferable to stopping the operation of the rear stageultraviolet radiation device 10.

On the other hand, the ultraviolet transmittance is subject toinfluences by floating matters, turbidity matters and dissolved organicmatters in the raw water. For this reason, when the raw water turbidityincreases owing to rainfalls and the like, the ultraviolet transmittancedecreases greatly. In such a case, the controller 14 makes a control tostop the operation of the front stage ultraviolet radiation device 5, orto decrease the output of the ultraviolet lamps to the lower limitvalue. This is because when the ultraviolet transmittance decreasesgreatly, the necessary ultraviolet amount may not be obtained even withthe maximum radiation of the front stage ultraviolet radiation device 5in some cases, and there is a high possibility that the electric powercharged to the front stage ultraviolet radiation device 5 may be wasted.

In this case, the controller 14 makes control to change flow routes byoperating the three-way valves 7 a, 7 b to cause the raw water to flowin the bypass piping 6 in order to prevent the piping inside frombecoming dirty owing to the deposition of floating matters and turbiditymatters and the attachment of organic matters. Further, the controller14 increases the output of the rear stage ultraviolet radiation device10 over a standard value, and compensates the loss of the sterilization(disinfection) performance of microbes in the front stage process.

(Control of Rear Stage Ultraviolet Radiation Device 10)

Next, a method of controlling a radiation amount of the rear stageultraviolet radiation device 10 will be explained hereinafter.

The rear stage ultraviolet radiation device 10 is arranged at the rearstage of the coagulation/sedimentation basin 3, and radiates ultravioletlight into sedimented water as treatment water. Part of floating mattersand turbidity matters, and algae and pathogenic microbes in the rawwater are taken into flocks and deposited, and are removed as pollutedsludge. However, organic matters dissolved in the water cannot beremoved by the coagulation/sedimentation process performed at 3.Therefore, they are left as ultraviolet absorbing factors in the rearstage ultraviolet radiation device 10.

The controller 14 controls the output of the ultraviolet lamps in therear stage ultraviolet radiation device 10 in order to obtain aradiation by the ultraviolet amount necessary to deaden or inactivateplural microbes left after the coagulation/sedimentation process.

The controller 14 controls the output of the ultraviolet lamps of therear stage ultraviolet radiation device 10 in consideration of theultraviolet transmittance of the sedimented water by the sedimentedwater ultraviolet transmissometer 18, the flow rate measurement value bythe sedimented water flow meter 9, an ultraviolet illuminancedistribution defined by the arrangement of the ultraviolet lamps in therear stage ultraviolet radiation device 10, and the flowing conditionthat changes depending on the flow route structure and the flow rate, byuse of the arithmetic equations such as the above arithmetic equations(1) to (2). More specifically, the controller 14 calculates a necessaryultraviolet output value according to the ultraviolet transmittance andthe flow rate change by the arithmetic equations. Thereby, thecontroller controls the electric power supplied from the ultravioletlamp power source 13 b to the ultraviolet lamps in the rear stageultraviolet radiation device 10.

In brief, the system according to the present embodiment controls andperforms the ultraviolet radiation treatment by the front stageultraviolet radiation device 5 at the front stage process, and theultraviolet radiation treatment by the rear stage ultraviolet radiationdevice 10 at the rear stage process, respectively. Accordingly, by theultraviolet radiation effect at the front stage process, the treatmentto make the microbes including algae and the like inactive or harmlessis realized, and by the ultraviolet radiation effect at the rear stageprocess, the treatment to make the microbes left still after thecoagulation/sedimentation process dead or inactive is realized.

Consequently, in water treatment systems especially of water systems andthe like, it is possible to attain the ultraviolet radiation effect, andthereby perform the countermeasures against algae and the sterilization(disinfection) treatment of pathogenic microbes and the like safely andsecurely. Further, in the system according to the present embodiment, itis possible to reduce greatly the use amount of chlorine agents injectedin the water purifying treatment process in the prior art. As a result,it is possible to prevent the occurrence of harmful by-product matterssuch as trihalomethanes generated in the course of the sterilizationwith chlorine agents. Furthermore, it is also possible to reduce thecosts required for the injection of chlorine agents.

Second Embodiment

FIG. 2 is a block diagram showing major portions of a water treatmentsystem according to a second embodiment of the invention.

The system according to the present embodiment has a raw water turbiditymeter 21 and a raw water fluorescence analyzer 23 as raw waterultraviolet transmittance measuring devices, and also has a sedimentedwater fluorescence analyzer 24 as a sedimented water ultraviolettransmittance measuring device. Meanwhile, the same functionalcomponents as those of the system according to the first embodimentshown in FIG. 1 are denoted by the same reference numerals, and thedetailed description thereof is omitted.

In the system according to the present embodiment, a turbidity of rawwater measured by the raw water turbidity meter 21 is input to acontroller 14, and a fluorescence intensity of raw water measured by theraw water fluorescence analyzer 23 is also input to the controller 14.Further, a fluorescence intensity of sedimented water measured by thesedimented water fluorescence analyzer 24 is input to the controller 14.

The raw water turbidity meter 21 measures a turbidity of a raw watersample taken up by a raw water sampling pipe 15. Herein, the raw watersampling pipe 15 is connected to a piping for connecting a water basin 2and a front stage ultraviolet radiation device 5.

The raw water fluorescence analyzer 23 measures a fluorescence intensityof a raw water sample taken up by the raw water sampling pipe 15 andfiltered by a filtration device 22.

On the other hand, the sedimented water fluorescence analyzer 24measures the fluorescence intensity of a sedimented water sample takenup by a sedimented water sampling pipe 17. Herein, the sedimented watersampling pipe 17 is connected to a piping between acoagulation/sedimentation basin 3 and a rear stage ultraviolet radiationdevice 10.

Meanwhile, in the raw water fluorescence analyzer 23, it is necessary toremove turbidity matters in order to precisely measure dissolved organicmatters in raw water. Therefore, the filtration device 22 is arranged atthe front stage of the raw water fluorescence analyzer 23 to therebyremove turbidity matters in raw water. Conversely, with regard to thesedimented water measured by the sedimented water fluorescence analyzer24, turbidity matters are removed at the coagulation/sedimentation basin3, and thus, there is no need for arranging a filtration device.

(Operation and Effects of Second Embodiment)

Hereinafter, the operation and effects of the present embodiment will beexplained with reference to FIGS. 2 and 3 to 5.

In general, when ultraviolet penetrates water, the ultraviolet intensityis attenuated by the absorption and scattering of turbidity matters suchas particles floating in water, the absorption by organic mattersdissolved in water, and the like. More specifically, the ultravioletintensity decreases as ultraviolet goes away from the radiation surface.The ultraviolet transmittance (%) shows a ratio of ultravioletpenetrating a clearance of 1 cm. Herein, examples of a device formeasuring the ultraviolet transmittance include the ultraviolettransmissometers 16, 18 as shown in FIG. 1.

However, a general ultraviolet transmissometer has a configuration forputting sample water in a quartz glass standard cell to measure anultraviolet transmittance in batch, or a configuration for causingsample water to flow in a quartz glass cell and measuring an ultraviolettransmittance in real time. In the configuration for measuring in batch,it is impossible to set the ultraviolet transmittance as a control indexof the ultraviolet lamp output. Further, in the configuration forcausing sample water to flow, it is impossible to correctly measure theultraviolet transmittance owing to dirt on the surface of the quartzglass cell.

The system according to the present embodiment has a configuration inwhich the ultraviolet transmittance is estimated on the basis ofmeasurement results of the turbidity of raw water and the concentrationof dissolved organic matters without using a general ultraviolettransmissometer.

The ultraviolet transmittance is composed of attenuation componentsowing to the absorption and scattering by turbidity matters floating inwater, and attenuation components owing to the absorption of organicmatters dissolved in water. Accordingly, by measuring the turbidity ofraw water and the concentration of dissolved organic matters, theultraviolet transmittance can be estimated.

FIG. 3 is a graph showing the relation between the turbidity of rawwater, and the ultraviolet transmittance in the case of considering onlyinfluences by the absorption and scattering owing to turbiditycomponents. As shown in FIG. 3, there is a correlation between theturbidity and the ultraviolet transmittance, and a relation as shown inthe following equation (3) is established:T _(tu) =f(tu)(%)  (3)

where T_(tu) means an ultraviolet transmittance (%) in the case whereultraviolet absorption/scattering manners are only turbidity matters,and tu means a turbidity (degree).

Further, there is ultraviolet absorbance as an index showing absorptionby dissolved organic matters in water. The relation between theultraviolet absorbance and the ultraviolet transmittance is defined bythe following equation (4):α_(oc)=−ln(T _(oc)/100)  (4)

where α_(oc) means an ultraviolet absorbance, and T_(oc) means anultraviolet transmittance (%) in the case of considering only absorptionby dissolved organic matters. Accordingly, measuring the ultravioletabsorbance enables to obtain the ultraviolet transmittance.

The controller 14 according to the present embodiment inputs afluorescence intensity of raw water measured by the raw waterfluorescence analyzer 23 and thereby calculates an ultravioletabsorbance, and estimates the concentration of dissolved organic mattersin raw water from the ultraviolet absorbance (refer to FIG. 4).

FIG. 4 is a graph showing the result of a measurement of the relationbetween a fluorescence intensity of a fluorescence wavelength 425 nmthat generates in response to an excitation wavelength 345 nm and anultraviolet absorbance by use of river water. As shown in FIG. 4, thereis a linear correlation between the fluorescence intensity (excitationwavelength 345 nm, fluorescence wavelength 425 nm) and the ultravioletabsorbance (wavelength 253.7 nm).

It has been confirmed that the concentration of dissolved organic carbon(DOC) as an index of the concentration of dissolved organic matters andthe fluorescence intensity at this moment has an extremely strongcorrelation, as shown in FIG. 5. From this fact, by measuring thefluorescence intensity with the raw water fluorescence analyzer 23, theultraviolet transmittance Toc (the value in the case of considering onlythe absorption by dissolved organic matters) can be calculated from therelation between FIG. 4 and the above equation (4), as shown in thefollowing equation (5):T _(oc)=100×exp(−c×FL)(%)  (5)

where c means a coefficient, and FL means a fluorescence intensity.

From the above, the total ultraviolet transmittance T in considerationof the absorption and scattering by the turbidity matter and dissolvedorganic matters in raw water can be obtained by the following equation(6).T=T _(tu) +T _(oc)(%)  (6)

The controller 14 calculates the ultraviolet transmittance of raw waterby use of the raw water turbidity measured by the raw water turbiditymeter 21, and the fluorescence intensity measured by the raw waterfluorescence analyzer 23. As explained in the above-described firstembodiment, the controller 14 controls the output of the ultravioletlamps of the front stage ultraviolet radiation device 5 on the basis ofthe ultraviolet transmittance of raw water. Consequently, unwasted andappropriate electric power is supplied to the front stage ultravioletradiation device 5, whereby it is possible to realize a completealgicidal effect of algae and sterilization (disinfection) of pathogenicmicrobes from raw water.

Further, in the same manner as in the first embodiment, the ultraviolettransmittance is subject to influences by floating matters, turbiditymatters and dissolved organic matters in the raw water. For this reason,when the raw water turbidity increases owing to rainfalls and the like,the ultraviolet transmittance decreases greatly. In such a case, thecontroller 14 makes a control to stop the operation of the front stageultraviolet radiation device 5, or to decrease the output of theultraviolet lamps to the lower limit value. In this case, the controller14 makes a control to change flow routes by operating the three-wayvalves 7 a, 7 b to cause the raw water to flow in the bypass piping 6 inorder to prevent the piping inside from becoming dirty owing to thedeposition of floating matters and turbidity matters and the attachmentof organic matters. Moreover, the controller 14 increases the output ofthe rear stage ultraviolet radiation device 10 over a standard value,and compensates the loss of the sterilization (disinfection) performanceof microbes in the front stage process.

Next, a method of controlling the rear stage ultraviolet radiationdevice 10 will be explained hereinafter.

The rear stage ultraviolet radiation device 10 is arranged at the rearstage of the coagulation/sedimentation basin 3, and radiates ultravioletto sedimented water as treatment water. In this case, turbidity mattershave been removed from the treatment water. Therefore, the controller 14can calculate the ultraviolet transmittance of the sedimented water fromthe relation of the above equation (5) on the basis of the fluorescenceintensity measured by the deposition fluorescence analyzer 24.

Accordingly, the controller 14 controls the output of the ultravioletlamps so as to secure the necessary ultraviolet amount in the rear stageultraviolet radiation device 10 on the basis of the ultraviolettransmittance of the sedimented water and the flow rate measured by thesedimented water flow meter 9. Consequently, it is possible to preciselyperform the sterilization of pathogenic microbes. Further, wastedelectricity consumption can be prevented.

Third Embodiment

FIG. 6 is a block diagram showing major portions of a water treatmentsystem according to a third embodiment of the invention.

The system according to the present embodiment relates to an ultravioletradiation control using ultraviolet illuminance meters 19, 20 arrangedin a front stage ultraviolet radiation device 5 and a rear stageultraviolet radiation device 10, respectively. Meanwhile, the samefunctional components as those of the system according to the firstembodiment shown in FIG. 1 are denoted by the same reference numerals,and the detailed description thereof is omitted.

As shown in FIG. 6, the system according to the present embodiment hasthe ultraviolet illuminance meters 19, 20 arranged in the front stageultraviolet radiation device 5 and the rear stage ultraviolet radiationdevice 10, respectively. Respective measurement results from theultraviolet illuminance meters 19, 20 are input to a controller 14.

FIG. 7 is a diagram showing an internal configuration of the front stageultraviolet radiation device 5 for use in the system according to theembodiment, and shows a case where ultraviolet lamps 27 are arranged inthe direction perpendicular to the flow direction of treatment water.Meanwhile, the internal configuration is also same in the case of therear stage ultraviolet radiation device 10.

Herein, the front stage ultraviolet radiation device 5 and the rearstage ultraviolet radiation device 10, as shown in FIG. 7, have aplurality of ultraviolet lamps 27 therein, and also have ultravioletlamp protective tubes 28 made of quartz glass for protecting therespective ultraviolet lamps 27. Further, the front stage ultravioletradiation device 5 and the rear stage ultraviolet radiation device 10have cleaning brush members 29 for cleaning the protective tubes 28. Thecleaning brush member 29 is driven by a cleaning driving device 25(however, a cleaning driving device 26 in the rear stage ultravioletradiation device 10). The cleaning driving devices 25, 26 are controlledby the controller 14.

The controller 14 according to the embodiment is configured so as toperform an output control of the respective ultraviolet lamps 27 in theultraviolet radiation devices 5, 10 by use of the ultravioletilluminance meters 19, 20, an operation control of the cleaning brushmembers 29 of the ultraviolet lamp protective tubes 28, and performancemonitoring of the ultraviolet lamps 27. These operations will bespecifically explained hereinafter.

(Output Control of Ultraviolet Lamps 27)

The controller 14 controls the output of the ultraviolet lamps 27 builtin the front stage ultraviolet radiation device 5 by means of thecontrol method explained in the above-described first or secondembodiment. Herein, when a measurement value is input to the controller14 from the ultraviolet illuminance meter 19, an ultraviolet illuminancein the inside of the front stage ultraviolet radiation device 5 can bealways monitored.

On the other hand, an ultraviolet amount target value Dose_(targ)necessary to deaden or inactivate microbes to be treated (algae orpathogenic microbes, etc.) is preset (stored) in the controller 14.Further, in the controller 14, an arithmetic equation (7) forcalculating a retention time t from a measurement value F_(R) Of the rawwater flow meter 4 and the flow route structure of the front stageultraviolet radiation device 5 is set, and an arithmetic equation (8)for calculating an ultraviolet amount target value I_(targ) at the setposition of the ultraviolet illuminance meter 19 from the ultravioletamount target value Dose_(targ) and the retention time t is set:t=(S×L)/F _(R)(s)  (7)

where F_(R) is a measurement value (m³/s) by the raw water flow meter; Sis a representative flow route cross sectional area (m²); and L is arepresentative flow route length (m):I _(targ) =C _(t)×(Dose _(targ) /t)(mW/cm₂)  (8)

where C_(t) is a correction coefficient, which is determined by therelation of an equation (9) on the basis of a positional relationconstant K_(t) of the ultraviolet illuminance meter 19 and theultraviolet lamp 27, and a measurement value T_(R) by the raw waterultraviolet transmissometer 16.C _(t) =K _(t) ×f(T _(R))  (9)

The controller 14 compares “I_(meas)” and “I_(targ)” by use of the abovearithmetic equation (8) and a measurement value I_(meas) by theultraviolet illuminance meter 19. When the comparison result is“I_(meas)<I_(targ)”, the controller 14 controls so as to increase theoutput of the ultraviolet lamp 27. When the comparison result is“I_(meas)>I_(targ)”, the controller 14 controls so as to decrease theoutput of the ultraviolet lamp 27.

Meanwhile, the controller 14 performs the same output control also tothe ultraviolet lamps 27 of the rear stage ultraviolet radiation device10.

(Cleaning Control of Ultraviolet Lamp Protective Tubes and RadiationPerformance Monitoring of Ultraviolet Lamps)

The controller 14 according to the embodiment has set therein: anarithmetic equation (10) for calculating an ultraviolet illuminanceI_(o) at the surface of the ultraviolet lamp protective tube 28 at thetime of the output of the ultraviolet lamp 27; an arithmetic equation(11) for calculating an ultraviolet illuminance I_(m0) at the surface ofthe ultraviolet lamp protective tube 28 from the measurement valueI_(meas) by the ultraviolet illuminance meter 19; and an allowable valueΔI_(f) of a difference between I₀ and I_(m0) “ΔI=I₀−I_(m0)”:I ₀=η_(UV) ×w/W(mW/cm²)  (10)provided that η_(UV)=f(w)

where W means an ultraviolet lamp constant input electricity (W); wmeans an ultraviolet lamp input electricity set value (W); and η_(UV)means an ultraviolet output efficiency (%):I _(m0) =f(K _(m0) , I _(meas) , T _(R))(mW/cm²)  (11)

where K_(m0) is a constant determined by the positional relation betweenthe ultraviolet lamp 27 and the ultraviolet illuminance meter 19;I_(meas) means a measurement value (mW/cm²) by the ultravioletilluminance meter 19; and T_(R) means a raw water ultraviolettransmittance (%).

The controller 14 compares the difference between I₀ and I_(m0)“difference ΔI=I₀−I_(m0)” calculated by the above arithmetic equations(10) and (11) with “ΔI_(f)”. When the comparison result is “ΔI≧ΔI_(f)”,the controller 14 controls the cleaning driving device 25 so as tooperate the cleaning brush 29 of the ultraviolet lamp protective tube28.

Next, the operation of radiation performance monitoring of theultraviolet lamp will be explained.

The ultraviolet generation efficiency of the ultraviolet lamp 27decreases with time according to an individual lamp characteristic.Therefore, it is necessary to exchange the ultraviolet lampsperiodically. Thus, when the controller 14 determines that there hasoccurred deterioration exceeding the allowable range with theultraviolet lamp 27, the controller makes a control to output a displayso as to display prompting exchange of the ultraviolet lamps 27 from adisplay device or the like.

More specifically, a surface illuminance initial value I_(ini) of theultraviolet lamp protective tube 28, and an allowable value ΔI_(ini) ofthe lamp performance decrease are set in the controller 14. Immediatelyafter operating the cleaning brush member 29 of the ultraviolet lampprotective tube 28, the controller 14 calculates the surface ultravioletilluminance I_(m0) of the ultraviolet lamp protective tube 28 from themeasurement value I_(meas) by the ultraviolet lamp illuminance meter 19by use of the above arithmetic equation (11). The controller 14 comparesthe difference between the calculated value and the preset initialilluminance I_(ini) “ΔIc=I_(ini)−I_(m0)” with the allowable valueΔI_(ini) of the lamp performance decrease. When the comparison result is“ΔI_(c)>ΔI_(ini)”, the controller performs a display output to prompt toexchange the ultraviolet lamps 27.

Immediately after the exchange of the ultraviolet lamps 27, it must bethat “ΔI_(c)=0”. However, there is actually unevenness in the initialperformance of the ultraviolet lamp 27, and thus, the performanceallowable value of a new lamp is set ΔI_(ini,0). In addition, when thecomparison result immediately after the exchange of the ultravioletlamps 27 is “ΔI_(c)>ΔI_(ini,0)”, the controller 14 gives an alarminforming of an error with the protective tube 28, the deterioration ofthe cleaning brush 29, a fault with other devices, and the like.Further, the controller performs a display output to display a messageprompting to do a comprehensive maintenance including exchange of theprotective tubes 28 and exchange of the cleaning brushes 29.

Meanwhile, the controller 14 performs the same monitoring control alsoto the ultraviolet lamps 27 of the rear stage ultraviolet radiationdevice 10.

In short, according to the system of the present embodiment, it ispossible to judge the excess and deficiency of the ultraviolet amount onthe basis of the respective measurement values by the ultravioletilluminance meters 19, 20 arranged in the front stage ultravioletradiation device 5 and the rear stage ultraviolet radiation device 10,and to correct and control the output of the ultraviolet lamps 27 byfeedback. Moreover, by monitoring the dirt condition on the surface ofthe ultraviolet lamp protective tube 28, and monitoring the decrease ofthe ultraviolet generation efficiency of the ultraviolet lamps 27, it ispossible to perform the operation control of the cleaning brush member29 of the ultraviolet lamp protective tube 28, and the lamp maintenancesupport. As a consequence, it is possible to realize a water treatmentsystem that automatically performs the maintenance of a stableultraviolet radiation performance, and the maintenance of theultraviolet radiation devices 5, 10.

Fourth Embodiment

FIG. 8 is a schematic diagram showing a water treatment system accordingto a fourth embodiment of the invention and a water purifying plant towhich the water treatment system is applied.

In the water purifying plant, for example, a sand basin 52 and a waterbasin 53, a flock-forming basin 54, a sedimentation basin 55, a middlemixing basin 56, a filter basin 57, a chlorine mixing basin 58, and adistributing reservoir 59 are arranged from the upstream side of a flowroute of raw water 51 supplied from a river to the downstream side.Further, in the course where the raw water 51 flows in the aboverespective basins 52 to 59, predetermined water treatments are carriedout in the respective basins. Thereby, the raw water 51 is made intodrinkable purified water 60, which is sent out from the distributingreservoir to respective water customers.

Specific procedures of water treatment will be explained hereinafter.

First, in the sand basin 52, large sands and dirts included initially inthe raw water 51 are sent to the bottom. Thus, treatment water fromwhich large sands and dirts have been removed flows into the water basin53. When the treatment water flows from the sand basin 52 to the waterbasin 53, a “flow rate” of the treatment water is measured by a flowmeter 61 a. A measurement value of the flow rate is input to a frontstage injection and radiation control unit 63. When the treatment waterflows from the sand basin 52 to the water basin 53, a “turbidity” of thetreatment water is measured by a turbidity measuring unit 64 a. Ameasurement value of the turbidity is input to the front stage injectionand radiation control unit 63.

Sodium hypochlorite of an amount designated by the front stage injectionand radiation control unit 63 is injected to the water basin 53 via Nunits of injection pumps 65 a. Further, to the water basin 53,ultraviolet of an amount designated by the front stage injection andradiation control unit 63 is radiated by N pieces of UV (ultraviolet)lamps 66 a. Namely, the water basin 53 becomes a front stage injectionand radiation point of sodium hypochlorite and ultraviolet. In additionto the above sodium hypochlorite, sodium hydroxide 67 a is injected tothe above water basin 53. With the sodium hydroxide 67 a, the sodiumhypochlorite and the ultraviolet, algicidal treatment and sterilizationto algae and microbes included in the treatment water in the water basin53 are carried out.

The turbidity measuring unit 64 a incorporates: a turbidity meter formeasuring the turbidity of the treatment water from the clarity of thetreatment water in the water basin 53; a fine particle counter forcounting the number of fine particles floating in the treatment water inthe water basin 53; a fluorescence analyzer for detecting, for example,biological information of algae; and a UV (ultraviolet) meter fordetecting a living matter by radiating ultraviolet of a wavelength, forexample, 730 nm.

The purpose of injecting and radiating the sodium hypochlorite and theultraviolet is algicidal treatment and sterilization to algae andmicrobes included in the treatment water. Herein, at a mass generationof algae and the like included in the treatment water, the turbidityincreases. Thus, according to this turbidity, the target injection andradiation amount of the sodium hypochlorite and the ultraviolet is set.Namely, the “turbidity” sent from the turbidity measuring unit 64 a tothe front stage injection and radiation control unit 63 is the turbidityobtained by extracting algae and microbes as the main components fromamong the turbidity components shown by algae and diatoms,cyanobacteria, germs and sands and mud matters. More specifically, it isthe turbidity obtained by correcting the optical turbidity determinedfrom the clarity of the treatment water by use of respective measurementvalues of the fine particle counter, the fluorescence analyzer, and theUV (ultraviolet) meter.

Meanwhile, from the viewpoint of construction costs and the like, theturbidity measuring unit 64 a may be configured by only a turbiditymeter that measures the turbidity of the treatment water from theclarity of the treatment water.

The treatment water after the front stage (first) sterilization andalgicidal treatment at the water basin 3 flows via a flow meter 61 b anda turbidity measuring unit 64 b to the flock-forming basin 54. Polyaluminum chloride (so-called PAC 68 a) is injected into the treatmentwater in the flock-forming basin 54. Impurities included in thetreatment water are solidified by the PAC 68 a. This makes it possibleto remove impurities included in the treatment water. Thereafter, thetreatment water flows into the sedimentation basin 55 as a middle stagebasin. The flow rate measured by the flow meter 61 b is sent to a middlestage injection and radiation control unit 69. The turbidity measured bythe turbidity measuring unit 64 b is also sent to the middle stageinjection and radiation control unit 69.

Sodium hypochlorite of an amount designated by the middle stageinjection and radiation control unit 69 is injected to the sedimentationbasin 55 via N units of injection pumps 65 b. Further, to thesedimentation basin 55, ultraviolet of an amount designated by themiddle stage injection and radiation control unit 69 is radiated by N UV(ultraviolet) lamps 66 b. Therefore, the sedimentation basin 55 becomesa middle stage injection and radiation point of sodium hypochlorite andultraviolet. In addition to the above sodium hypochlorite, sodiumhydroxide 67 b is injected to the sedimentation basin 55. With thesodium hydroxide 67 b, the sodium hypochlorite and the ultraviolet,algicidal treatment and sterilization to algae and microbes included inthe treatment water in the sedimentation basin 55 are carried out. Inthe sedimentation basin 55, fine particles included in the treatmentwater are deposited.

The treatment water after the middle stage (second) sterilization andalgicidal treatment at the sedimentation basin 55 is added with PAC 86 bin the next middle mixing basin 56. Thereafter, filtration is carriedout in the next filter basin 57.

In the filter basin 57, the treatment water after filtration flows via aflow meter 61 c and a turbidity measuring unit 64 c to a chlorine mixingbasin 58. A measurement value of the flow rate measured by the flowmeter 61 c is sent to a rear stage injection and radiation control unit70. A measurement value of the turbidity measured by the turbiditymeasuring unit 64 c is also sent to the rear stage injection andradiation control unit 70.

Sodium hypochlorite of an amount designated by the rear stage injectionand radiation control unit 70 is injected to the chlorine mixing basin58 via N units of injection pumps 65 c. Further, to the chlorine mixingbasin 58, ultraviolet of an amount designated by the rear stageinjection and radiation control unit 70 is radiated by N UV(ultraviolet) lamps 66 c. Thus, the chlorine mixing basin 58 becomes arear stage injection and radiation point of sodium hypochlorite andultraviolet.

Further, sodium hydroxide 67 c is injected to the treatment water in thechlorine mixing basin 58. In the chlorine mixing basin 58, the contentof chlorine included in the treatment water is adjusted, and a thirdalgicidal treatment and sterilization is carried out by use of thesodium hydroxide 17 c, the sodium hypochlorite and the ultraviolet.Thereafter, the treatment water is stored in the distributing reservoir59. The stored treatment water is distributed as purified water 60 torespective customers.

FIG. 9 is a block diagram showing a schematic configuration of amonitoring control unit 62 including a computer in the water treatmentsystem. An injection and radiation control pattern table 71, aninput/output unit 74 including a display unit 72 and an operating unit73, and a raw water turbidity determining unit 75 are provided in themonitoring control unit 62. Meanwhile, the operating unit 73 includes akeyboard and a mouse.

The injection and radiation control pattern table 71 has stored thereindata showing the treatment methods according to the turbidities in thewater basin 53, the sedimentation basin 55, and the chlorine mixingbasin 58. Specifically, as shown in FIG. 10, there are set respectiveturbidity ranges 81 a, 81 b and 81 c, that is, the high turbidity(turbidity of 10 or higher, turbidity range 81 a), the middle turbidity(turbidity of 5 or higher and lower than 10, turbidity range 81 b), andthe low turbidity (turbidity lower than 5, turbidity range 81 c) withrespect to the measurement value of the turbidity of the raw water 51input from the turbidity measuring unit 64 a in FIG. 8. A controlpattern 82 for the sodium hypochlorite injection treatment or theultraviolet radiation treatment is preset in response to the respectiveturbidity ranges 81 a, 81 b and 81 c and the front stage unit (the waterbasin 53), the middle stage unit (the sedimentation basin 55), and therear stage unit (the chlorine mixing basin 58).

For example, when the turbidity of the raw water 51 is at the highturbidity of 10 or higher (turbidity range 81 a), the front stageinjection and radiation control unit 63 performs the algicidal treatmentand sterilization to the treatment water in the front stage water basin53 by use of only sodium hypochlorite. Further, the middle stageinjection and radiation control unit 69 performs the algicidal treatmentand sterilization to the treatment water in the middle stagesedimentation basin 55 by use of only sodium hypochlorite. In addition,the rear stage injection and radiation control unit 70 performs thealgicidal treatment and sterilization to the treatment water in the rearstage chlorine mixing basin 58 by use of sodium hypochlorite andultraviolet.

When the turbidity of the raw water 51 is at the middle turbidity of 5or higher and lower than 10 (turbidity range 81 b), the front stageinjection and radiation control unit 63 performs the algicidal treatmentand sterilization to the treatment water in the front stage water basin53 by use of ultraviolet and sodium hypochlorite. Further, the middlestage injection and radiation control unit 69 performs the algicidaltreatment and sterilization to the treatment water in the middle stagesedimentation basin 55 by use of ultraviolet. In addition, the rearstage injection and radiation control unit 70 performs the algicidaltreatment and sterilization to the treatment water in the rear stagechlorine mixing basin 58 by use of only sodium hypochlorite.

Moreover, when the turbidity of the raw water 51 is at the low turbiditylower than 5 (turbidity range 81 c), the front stage injection andradiation control unit 63 performs the algicidal treatment andsterilization to the treatment water in the front stage water basin 53by use of only ultraviolet. Further, the middle stage injection andradiation control unit 69 performs the algicidal treatment andsterilization to the treatment water in the middle stage sedimentationbasin 55 by use of only ultraviolet. In addition, the rear stageinjection and radiation control unit 70 performs the algicidal treatmentand sterilization to the treatment water in the rear stage chlorinemixing basin 58 by use of sodium hypochlorite and ultraviolet.

The raw water turbidity determining unit 75 determines to which of theturbidity ranges 81 a, 81 b and 81 c the measurement value of theturbidity of the raw water 51 input from the turbidity measuring unit 64a at the front stage in FIG. 8 belongs. The raw water turbiditydetermining unit displays the determination result and turbidityinformation on the display unit 72. Further, the raw water turbiditydetermining unit sends the determination result to a control patternreading unit 76.

The control pattern reading unit 76 reads the respective controlpatterns 82 for the injection of sodium hypochlorite and the radiationof ultraviolet in the front stage unit, the middle stage unit, and therear stage unit belonging to the turbidity ranges 81 a, 81 b and 81 c.Then, the control pattern reading unit 76 sends the control patterns 82via an automatic/manual switching unit 78 and respective output units 80a, 80 b and 80 c to the corresponding front stage injection andradiation control unit 63, the middle stage injection and radiationcontrol unit 69, and the rear stage injection and radiation control unit70.

When the operation mode is set to the “manual mode”, the control patternsetting unit 77 sends out the control patterns 82 via theautomatic/manual switching unit 78 switched to the manual mode and therespective output units 80 a, 80 b and 80 c to the correspondinginjection and radiation control units 63, 69 and 70. Herein, an operatorrefers to the turbidity ranges 81 a, 81 b and 81 c of the raw water 51displayed on the display unit 72, and inputs the control patternscorresponding to the front stage injection and radiation control unit63, the middle stage injection and radiation control unit 69, and therear stage injection and radiation control unit 70, via the operatingunit 73.

Respective injection and radiation setting units 79 a, 79 b and 79 csend the injection amount of sodium hypochlorite or the radiation amountof ultraviolet to the front stage injection and radiation control unit63, the middle stage injection and radiation control unit 69, and therear stage injection and radiation control unit 70. For more details,the injection and radiation setting units send the amount of sodiumhypochlorite to be injected or the amount (set value) of ultraviolet tobe radiated to the treatment water in the front stage unit (the waterbasin 53), the middle stage unit (the sedimentation basin 55), and therear stage unit (the chlorine mixing basin 58), the amounts beingdesignated by the operator with the operating unit 73, to the frontstage injection and radiation control unit 63, the middle stageinjection and radiation control unit 69, and the rear stage injectionand radiation control unit 70 shown in FIG. 8 via the output units 80 a,80 b and 80 c.

FIG. 11 is a view showing a display screen 83 of the display unit 72 ofthe input/output unit 74. The display screen 83 has: control unitdesignation buttons 84 a, 84 b and 84 c for designating the front stageinjection and radiation control unit 63, the middle stage injection andradiation control unit 69, and the rear stage injection and radiationcontrol unit 70, respectively; control patter designation buttons 85 a,85 b and 85 c for designating three kinds of control patterns 82 of theabove-mentioned “sodium hypochlorite”, “ultraviolet” and “sodiumhypochlorite+ultraviolet”; and mode switching buttons 86 for switchingand designating the control modes of the front stage injection andradiation control unit 63, the middle stage injection and radiationcontrol unit 69, and the rear stage injection and radiation control unit70, respectively.

Meanwhile, two or more of the control pattern designation buttons 85 a,85 b and 85 c are not pressed at one time with respect to one of theinjection and radiation control units 63, 69 and 70. A “computer mode”,“automatic mode”, and “manual mode” can be selected as operation modes.

Further, in the display screen 83, there is arranged a set amount inputunit 87 for writing the injection amount of sodium hypochlorite and theradiation amount of ultraviolet when the “manual mode” is selected. Theset amount input unit 87 makes it possible for the operator to write theamount (injection amount per unit volume) of sodium hypochlorite to beinjected to the treatment water in the front stage unit (the water basin53), the middle stage unit (the sedimentation basin 55), and the rearstage unit (the chlorine mixing basin 58) and the amount (radiationamount per unit volume) of ultraviolet to be radiated thereto, throughoperation of the operating unit 75 such as a keyboard. Further, a rawwater turbidity 88 and a turbidity determination result 89 input fromthe raw water turbidity determining unit 75 are displayed in the displayscreen 83.

FIG. 12 is a block diagram showing a schematic configuration of thefront stage injection and radiation control unit 63. The middle stageinjection and radiation control unit 69 and the rear stage injection andradiation control unit 70 have substantially the same configuration asthat of the front stage injection and radiation control unit 63, andtherefore, explanations thereof are omitted herein.

When, in the operating unit 73, the “computer mode” or the “automaticmode” is designated by the mode switching buttons 86, and the controlpattern 82 of “sodium hypochlorite” is automatically designated to thefront stage injection and radiation control unit 63, the monitoringcontrol unit 62 inputs a drive command 96 a via the output unit 80 a toa sodium hypochlorite injection amount control unit 96. Because, in thiscase, the drive command 97 a is not input to a radiation amount controlunit 97 of ultraviolet, a radiation amount control unit 99 is notdriven. Therefore, no ultraviolet is radiated to the treatment water inthe water basin 53.

A turbidity/injection amount conversion unit 98 stores, as shown in FIG.13A, relation information between a measurement value of the turbidityof treatment water (raw water 51) made to flow into the water basin 53,and a target injection amount (SV) per unit volume of sodiumhypochlorite to be injected to the treatment water. In theturbidity/injection amount conversion unit 98, the input measurementvalue of the turbidity is converted into a value of an injection amount(SV) per unit volume of the sodium hypochlorite to be injected. Further,the converted value of the injection amount is sent to the injectionamount control unit 96.

The injection amount control unit 96 performs a feed forward control (FFcontrol). Specifically, the injection amount control unit 96 sends theinjection amount (injection amount per unit time) obtained bymultiplying the target injection amount (SV) per unit volume by themeasurement value of the flow rate (PV) by the flow meter 61 a to aninjection pump driving unit 100. The injection pump driving unit 100drives the number of injection pumps 65 c according to the injectionamount. As a result, sodium hypochlorite of the amount corresponding tothe “turbidity” is injected to the treatment water in the water basin53.

When, in the operating unit 73, the “computer mode” or the “automaticmode” is designated by the mode switching buttons 86, and the controlpattern 82 of “ultraviolet” is automatically designated to the frontstage injection and radiation control unit 63, the monitoring controlunit 62 inputs a drive command 97 a via the output unit 80 a to anultraviolet radiation amount control unit 97. On the other hand, themonitoring control unit does not input the drive command 96 a via theoutput unit 80 a to the sodium hypochlorite injection amount controlunit 96. Therefore, the injection amount control unit 96 is not driven,so that sodium hypochlorite is not injected to the treatment water inthe water basin 53.

A turbidity/radiation amount conversion unit 99 stores, as shown in FIG.13B, relation information between a measurement value of the turbidityof treatment water (raw water 51) made to flow into the water basin 53,and a target radiation amount (SV) per unit volume of ultraviolet to beradiated to the treatment water. In the turbidity/radiation amountconversion unit 99, the input measurement value of the turbidity isconverted into a value of the radiation amount (SV) per unit volume ofultraviolet to be radiated. Further, the converted value of theradiation amount is sent to the radiation amount control unit 97.

The radiation amount control unit 97 sends the radiation amount(radiation amount per unit time) obtained by multiplying the targetinjection amount (SV) per unit volume by the measurement value of theflow rate (PV) by the flow meter 61 a to an UV lamp quantity settingunit 101. In the UV lamp quantity setting unit 101, as shown in FIG.13C, relation information between the above multiplied radiation amountand the number of UV lamps 66 a to be lit is stored. In the UV lampquantity setting unit 101, the number of UV lamps 66 a corresponding tothe radiation amount designated from the radiation amount control unit97 are lit. Thereby, ultraviolet of the amount corresponding to themeasurement value of the turbidity is radiated to the treatment water inthe water basin 53.

When, in the operating unit 73, the “computer mode” or the “automaticmode” is designated by the mode switching buttons 86, and the controlpattern 82 of “sodium hypochlorite+ultraviolet” is automaticallydesignated to the front stage injection and radiation control unit 63,the monitoring control unit 62 inputs the drive command 96 a via theoutput unit 80 a to the sodium hypochlorite injection amount controlunit 96. Further, in this case, the monitoring control unit inputs thedrive command 97 a to the ultraviolet radiation amount control unit 97.

In the state where both of the injection amount control unit 96 and theradiation amount control unit 97 work, the injection of sodiumhypochlorite and the radiation of ultraviolet are carried out to thetreatment water in the water basin 53. For more details, the injectionamount and the radiation amount separately designated in the injectionamount control unit 96 and the radiation amount control unit 97 arechanged into ½, respectively. The values of the injection amount and theradiation amount are sent to the injection pump driving unit 100 and theUV lamp quantity setting unit 101. This makes it possible to carry outthe injection of sodium hypochlorite of the amount and the radiation ofultraviolet corresponding to the turbidity with respect to the treatmentwater in the front stage water basin 53.

Heretofore, there has been the specific operation executed by the frontstage injection and radiation control unit 63 when, in the operatingunit 73, the “computer mode” or the “automatic mode” is designated bythe mode switching buttons 86, and the control patterns 82 of “sodiumhypochlorite”, “ultraviolet”, and “sodium hypochlorite+ultraviolet” arerespectively designated to the respective turbidity ranges 81 a (highturbidity), 81 b (middle turbidity), and 81 c (low turbidity).

The middle stage injection and radiation control unit 69 hassubstantially the same configuration as that of the front stageinjection and radiation control unit 63. Therefore, the specificoperation which is executed by the middle stage injection and radiationcontrol unit 69 with respect to the middle stage sedimentation basin 55when, in the operating unit 73, the “computer mode” or the “automaticmode” is designated by the mode switching buttons 86, and the controlpatterns 82 of “sodium hypochlorite”, “ultraviolet”, and “sodiumhypochlorite+ultraviolet” are respectively designated to the respectiveturbidity ranges 81 a (high turbidity), 81 b (middle turbidity), and 81c (low turbidity) of the “turbidity” of the raw water 51 in themonitoring control unit 62 are substantially same as that in the frontstage injection and radiation control unit 63 explained previously.

Further, the rear stage injection and radiation control unit 70 also hassubstantially the same configuration as that of the front stageinjection and radiation control unit 63. Therefore, the specificoperation of the injection of sodium hypochlorite and the radiation ofultraviolet executed by the rear stage injection and radiation controlunit 70 with respect to the chlorine mixing basin 58 are substantiallysame as that in the front stage injection and radiation control unit 63explained previously.

Thus, in the injection and radiation control pattern table 71, thecontrol patterns 82 of “sodium hypochlorite”, “ultraviolet”, and “sodiumhypochlorite+ultraviolet” are respectively set to the respectiveturbidity ranges 81 a (high turbidity), 81 b (middle turbidity), and 81c (low turbidity) of the raw water 51. Therefore, when, in the operatingunit 73, the “computer mode” or the “automatic mode” is designated bythe mode switching buttons 86, it is possible to automatically performthe injection of sodium hypochlorite and the radiation of ultraviolet tothe front stage water basin 53, the middle stage sedimentation basin 55,and the rear stage chlorine mixing basin 58 according to the controlpatterns 82 set in the injection and radiation control pattern table 71in the monitoring control unit 62.

Meanwhile, as shown in the set contents of the injection and radiationcontrol pattern table 71, in principle, the injection amount of sodiumhypochlorite is restricted, and the radiation amount of ultraviolet isincreased with respect to the front stage water basin 53. The injectionamount of sodium hypochlorite is increased, and the radiation amount ofultraviolet is restricted with respect to the rear stage chlorine mixingbasin 58. Thereby, it is possible to restrict the by-product matters(trihalomethanes generation) arising from the injection of the largeamount of sodium hypochlorite to the front stage water basin 53 as muchas possible. Namely, it is possible to improve the water quality safetyof the purified water 60 supplied from the water purifying plant tocustomers further more.

On the other hand, when the turbidity of the raw water 51 flowing intothe water purifying plant is high, the radiation amount of ultravioletto the front stage water basin 53 is decreased, and the injection amountof sodium hypochlorite to the front stage water basin 53 is increased.

Thus, on the basis of combinations of the respective stages of the frontstage, the middle stage, and the rear stage, and the turbidity ranges atthe respective stages, the ratios of the injection amount of sodiumhypochlorite and the radiation amount of ultraviolet at the respectivestages are adjusted. As a consequence, algicidal treatment andsterilization can be carried out more sufficiently.

Moreover, when the injection amount of sodium hypochlorite in the entirewater purifying plant is decreased, the chemical costs of sodiumhypochlorite and aggregating agent PAC (poly aluminum chloride: chemicalfor aggregating and removing turbidity matters in water) and the like.This makes it possible to reduce the running cost of the water purifyingplant.

Next, explanation will be given for the operation of the front stageinjection and radiation control unit 63, the middle stage injection andradiation control unit 69, and the rear stage injection and radiationcontrol unit 70 when the “manual mode” is selected by the mode switchingbuttons 86 in the operating unit 73.

Assuming that, in the operating unit 73, the “manual mode” is selectedby the mode switching buttons 86 of 62, the “front stage injection andradiation control unit 63” is designated by the control unit designatingbutton 84 a, and further the “sodium hypochlorite” is designated by thecontrol pattern designation button 85 a. In this case, a designationsignal 85 aa showing the control pattern 82 of the “sodium hypochlorite”becomes its high level state. The designation signal 85 aa is outputfrom the output unit 80 a of the monitoring control unit 62. Meanwhile,designation signals 85 bb, 85 cc showing the control patterns 82 of the“ultraviolet” and the “sodium hypochlorite+ultraviolet” remain at theirlow level states.

As a result, an AND gate 90 is established in the front stage injectionand radiation control unit 63, and a set value switching circuit 92 isswitched to its set injection amount side via an OR gate 91. The setinjection amount is written into the column “front stage injectionamount” in the set amount input unit 87 of the display screen 83, and issent out from the injection and radiation setting unit 79 a in FIG. 9.Namely, the set value of the injection amount of sodium hypochloritewhich has been set by the operator is sent to the injection amountcontrol unit 96.

When the “manual mode” is selected by the mode switching button 86 inthe operating unit 73, the injection amount control unit 96 sends theinjection amount (injection amount per unit time) obtained bymultiplying the flow rate measured by the flow rate 61 a by the setinjection amount per unit volume, to the injection pump driving unit100. In this case, the target injection amount with the convertedturbidity of the water basin 53 output from the turbidity/injectionamount conversion unit 98 is not used.

The injection pump driving unit 100 drives the number of injection pumps65 c corresponding to the injection amount. As a result, sodiumhypochlorite of the amount designated by the operator via the operatingunit 73 is injected to the treatment water of the water basin 53.

When, in the operating unit 73, the “manual mode” is selected by themode switching buttons 86, and the “front stage injection and radiationcontrol unit 63” is designated by the control unit designating button 84a while the “sodium hypochlorite” is pressed by the control patterndesignation button 85 a, the AND gate 93 is not established, and theoutput of the OR gate 94 is at its low level. Therefore, the set valueswitching circuit 95 switches to the initial value (=0) side.

When the “manual mode” is selected by the mode switching button 86, theradiation amount control unit 97 designates the radiation amount to theUV lamp quantity setting unit 101. Therefore, when the initial value is0, ultraviolet is not substantially radiated to the treatment water inthe water basin 53.

Namely, in the state where the “front stage injection and radiationcontrol unit” is selected by the control unit designating button 84 a,and the “sodium hypochlorite” is pressed by the control patterndesignation button 85 a, only sodium hypochlorite of the amountdesignated by the operator via the set amount input unit 87 is injectedto the treatment water in the water basin 53.

Further, when the “manual mode” is selected by the mode switchingbuttons 86, and the “front stage injection and radiation control unit”is designated by the control unit designating button 84 a while the“ultraviolet” is selected by the control pattern designation button 85a, the AND gate 90 is not established, and the output of the OR gate 91is at its low level. In this case, the set value switching circuit 92switches to the initial value (=0) side. As a result, for the samereason as that in the above-mentioned case of the radiation amountcontrol unit 97, no ultraviolet is radiated to the treatment water inthe water basin 53.

Conversely, when the AND gate 93 is established, the set value switchingcircuit 95 switches to the set radiation amount side via the OR gate 94.The set radiation amount is written into the column “front stageradiation amount” of the set amount input unit 87 in the display screen83, and is sent via the injection and radiation setting unit 79 a to theradiation amount control unit 97. Namely, the set value of ultravioletset by the operator is input to the radiation amount control unit 97.

When the “manual mode” is selected by the mode switching buttons 86, theradiation amount control unit 97 sends the radiation amount (radiationamount per unit time) obtained by multiplying the set radiation amountper unit volume by the measurement value of the flow rate by the flowmeter 61 a, to the UV lamp quantity setting unit 101. The UV lampquantity setting unit 101 turns on the number of UV lamps 66 a accordingto the radiation amount. In this case, the target radiation amount withthe converted turbidity of the water basin 53 output from theturbidity/radiation amount conversion unit 99 is not used.

That is, when the “front stage injection and radiation control unit” isselected by the control unit designating button 84 a, and the“ultraviolet” is selected by the control pattern designation button 85b, ultraviolet of the amount designated by the operator via the setamount input unit 87 is radiated to the treatment water in the waterbasin 53.

In addition, assuming that the “manual mode” is selected by the modeswitching buttons 86, the “front stage injection and radiation controlunit” is designated by the control unit designating button 84 a, and the“sodium hypochlorite+ultraviolet” is selected by the control patterndesignation button 85 a. In such a case, a designation signal 85 ccshowing the control pattern of the “sodium hypochlorite+ultraviolet”becomes its high level state. In this case, because the outputs of therespective OR gates 91, 94 are at their high level states, the set valueswitching circuits 92, 95 switch to the set injection amount side andthe set radiation side, respectively. As a result, both of the injectionamount control unit 96 and the radiation amount control unit 97 work.Sodium hypochlorite of the injection amount that the operator haswritten into the set amount input unit 87 on the display screen 83 isinjected to the treatment water in the water basin 53. Further,ultraviolet of the radiation amount that the operator has written intothe set amount input unit 87 is radiated to the treatment water in thewater basin 53.

In this case, sodium hypochlorite and ultraviolet are separatelyinjected or radiated. Therefore, the operator sets the set injectionamount and the set radiation amount to half respectively as standards incomparison with the case where the injection amount control unit 96 andthe radiation amount control unit 97 work in a single operation.

Heretofore, there has been explained the specific operation executed bythe front stage injection and radiation control unit 63 when, in theoperating unit 73, the “manual mode” is designated by the mode switchingbuttons 86, the “front stage injection and radiation control unit” isdesignated by the control unit designating button 84 a, one of “sodiumhypochlorite”, “ultraviolet”, and “sodium hypochlorite+ultraviolet” isdesignated by the control pattern designating buttons 85 a, 85 b, 85 c,and the “injection amount” of sodium hypochlorite and the “radiationamount” of ultraviolet are designated by the set amount input unit 87.

In the same operation procedures, the operator can operate the middlestage injection and radiation control unit 69 and the rear stageinjection and radiation control unit 70 indirectly via the operatingunit 73. Thereby, the injection of sodium hypochlorite and the radiationof ultraviolet of the amounts set arbitrarily at the operating unit 73can be made to the treatment water in the middle stage sedimentationbasin 55 and the treatment water in the rear stage chlorine mixing basin58.

By adopting the above-mentioned “manual mode”, it is possible totemporarily change the injection of sodium hypochlorite and theradiation of ultraviolet to the treatment water in the front stage waterbasin 53, the middle stage sedimentation basin 55, and the rear stagechlorine mixing basin 58 even when the condition of the raw water 51changes abruptly owing to a concentrated rainfall, or when the conditionof the raw water 51 changes owing to a continuation of days withabnormally high temperatures.

Meanwhile, in the “computer mode” and the “automatic mode”, theinjection of sodium hypochlorite and the radiation of ultraviolet of theamounts according to the measurement value of the turbidities of thetreatment water are carried out automatically with respect to thetreatment water in the front stage water basin 53, the middle stagesedimentation basin 55, and the rear stage chlorine mixing basin 58 inthe water purifying plant.

Herein, a further advantage in the operation of the water purifyingplant by using radiation to algae removal will be explained hereinafter.

As a precondition, by use of aggregating chemicals (aggregation agentsor pH adjusting agents, aggregation auxiliary agents), turbidity matters(suspended turbidity matters) are aggregated into flocks and thendeposited in order to decrease the turbidity of raw water in acoagulation/sedimentation facility in the water purifying field. Then,in a filter basin at the front stage, these aggregated turbidity mattersare removed by filtration in a sand filter basin and the like. In thispoint, blocking of the filter basin becomes conspicuous in a slow speedfilter basin, a fast speed filter basin and the like, and therefore, itis necessary to decrease the turbidity of raw water in prior to someextent. Therefore, coagulation/sedimentation becomes especiallyimportant for the operation of the water purifying plant.

As mentioned previously, algae included in raw water are the main causeof filter basin blocking disorder factors, and aggregating agents areused in order to remove these algae.

With regard to this, an algicidal treatment is performed by ultravioletand sodium hypochlorite before charging aggregating agents, whereby thecleaning cycle of the water purifying plant can be made longer.Therefore, it contributes to the reduction of the use amount ofaggregating agents, the reduction of annual chemical costs, and theprevention of the filter basin blocking. Thus, the use of ultraviolet toalgae removal is a significant advantage to those who perform a watertreatment (mainly companies, local governments).

The present invention is not limited to the embodiments described above,but the present invention may be embodied in other specific formswithout departing from the gift thereof. Further, by appropriatecombinations of plural constitutional elements disclosed in each of theembodiments, it is possible to extract various stages of invention,which is apparent to those skilled in the art. For example, even whensome constitutional elements are deleted from all the elements shown inthe embodiments. Furthermore, some elements over different embodimentsmay be combined appropriately.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. A water treatment system for performing a water purifying treatmentby use of ultraviolet radiation, comprising: a coagulation/sedimentationbasin-containing system comprising means to perform acoagulation/sedimentation treatment process mixing water being treatedwith an aggregating agent; a first ultraviolet radiation device whichradiates ultraviolet to a raw water in a front stage process of thecoagulation/sedimentation treatment process, the first ultravioletradiation device located to treat the raw water before entering thecoagulation/sedimentation basin; a second ultraviolet radiation devicecomprising ultraviolet lamps located to radiate ultraviolet to the watertreated in the front stage process in a rear stage process of thecoagulation/sedimentation treatment process, the second ultravioletradiation device located to treat the water downstream from thecoagulation/sedimentation basin; a raw water ultraviolet transmissometerwhich is located to measure an ultraviolet transmittance of the rawwater at the front stage process; a sedimented water ultraviolettransmissometer which is located to measure an ultraviolet transmittanceof sedimented water at the rear stage process; and a control systemcomprising a control unit which controls the first and secondultraviolet radiation devices, wherein the control system is operablesuch that the control unit is responsive to a measurement result of theraw water ultraviolet transmissometer showing a higher transmittancethan a preset reference value, so that the control unit makes a controlto decrease an output of the ultraviolet lamps built in the secondultraviolet radiation device to a lower limit value, and the controlunit is responsive to a measurement result of the raw water ultraviolettransmissometer showing a lower transmittance than the preset referencevalue, so that the control unit makes a control to stop the operation ofthe first ultraviolet radiation device, and to make the output of theultraviolet lamps built in the second ultraviolet radiation devicehigher than a standard value.
 2. A water treatment system according toclaim 1, wherein the second ultraviolet radiation device radiatesultraviolet to the water between the coagulation/sedimentation basin inthe coagulation/sedimentation treatment process and a filter basinincluded in the rear stage process.
 3. A water treatment systemaccording to claim 2, wherein the control unit controls an output ofultraviolet lamps built in the second ultraviolet radiation device onthe basis of a measurement result of the sedimented water ultraviolettransmissometer.
 4. A water treatment system according to claim 3,further comprising: an ultraviolet illuminance meter to measure anultraviolet illuminance in the inside of the first ultraviolet radiationdevice, wherein the control unit has arithmetic equations set forcalculating an ultraviolet amount target value based on an ultravioletradiation effect, and an ultraviolet illuminance target value based on aflow rate measurement value and retention time of the raw water and theultraviolet amount target value; and compares a measurement value of thefirst ultraviolet illuminance meter with the ultraviolet illuminancetarget value calculated by the arithmetic equations, the control unitbeing responsive to a comparison result showing that the ultravioletilluminance target value is higher, so that the control unit makes acontrol to increase an output of ultraviolet lamps in the firstultraviolet radiation device; and the control unit being responsive tothe comparison result showing that the ultraviolet illuminance targetvalue is lower, so that the control unit performs a control to decreasethe output of the ultraviolet lamps in the first ultraviolet radiationdevice.
 5. A water treatment system according to claim 3, furthercomprising: an ultraviolet illuminance meter to measure an ultravioletilluminance in the inside of the second ultraviolet radiation device,wherein the control unit has arithmetic equations set for calculating anultraviolet amount target value based on an ultraviolet radiationeffect, and an ultraviolet illuminance target value based on a flow ratemeasurement value and retention time of the raw water and theultraviolet amount target value; and compares a measurement value of theultraviolet illuminance meter with the ultraviolet illuminance targetvalue calculated by the arithmetic equations, the control unit beingresponsive to a comparison result showing that the ultravioletilluminance target value is higher, so that the control unit makes acontrol to increase an output of ultraviolet lamps in the secondultraviolet radiation device; and the control unit being responsive tothe comparison result showing that the ultraviolet illuminance targetvalue is lower, so that the control unit makes a control to decrease theoutput of the ultraviolet lamps in the second ultraviolet radiationdevice.
 6. A water treatment system according to claim 2, furthercomprising: a sedimented water fluorescence analyzer which measures afluorescence intensity of sedimented water the rear stage process,wherein the control unit controls an output of the ultraviolet lampsbuilt in the second ultraviolet radiation device on the basis of themeasurement result of the sedimented water fluorescence analyzer.
 7. Awater treatment system according to claim 6, further comprising: anultraviolet illuminance meter to measure an ultraviolet illuminance inthe inside of the first ultraviolet radiation device, wherein thecontrol unit has arithmetic equations set for calculating an ultravioletamount target value based on an ultraviolet radiation effect, and anultraviolet illuminance target value based on a flow rate measurementvalue and retention time of the raw water and the ultraviolet amounttarget value; and compares a measurement value of the ultravioletilluminance meter with the ultraviolet illuminance target valuecalculated by the arithmetic equations, the control unit beingresponsive to a comparison result showing that the ultravioletilluminance target value is higher, so that the control unit makes acontrol to increase an output of ultraviolet lamps in the firstultraviolet radiation device; and the control unit being responsive tothe comparison result showing that the ultraviolet illuminance targetvalue is lower, so that the control unit performs a control to decreasethe output of the ultraviolet lamps in the first ultraviolet radiationdevice.
 8. A water treatment system according to claim 6, furthercomprising: an ultraviolet illuminance meter to measure an ultravioletilluminance in the inside of the second ultraviolet radiation device,wherein the control unit has arithmetic equations set for calculating anultraviolet amount target value based on an ultraviolet radiationeffect, and an ultraviolet illuminance target value based on a flow ratemeasurement value and retention time of the raw water and theultraviolet amount target value; and compares a measurement value of theultraviolet illuminance meter with the ultraviolet illuminance targetvalue calculated by the arithmetic equation, the control unit beingresponsive to a comparison result showing that the ultravioletilluminance target value is higher, so that the control unit makes acontrol to increase an output of ultraviolet lamps in the secondultraviolet radiation device; and the control unit being responsive tothe comparison result showing that the ultraviolet illuminance targetvalue is lower, so that the control unit makes a control to decrease theoutput of the ultraviolet lamps in the second ultraviolet radiationdevice.
 9. A water treatment system according to claim 2, furthercomprising: an ultraviolet illuminance meter to measure an ultravioletilluminance in the inside of the first ultraviolet radiation device,wherein the control unit has arithmetic equations set for calculating anultraviolet amount target value based on an ultraviolet radiationeffect, and an ultraviolet illuminance target value based on a flow ratemeasurement value and retention time of the raw water and theultraviolet amount target value; and compares a measurement value of theultraviolet illuminance meter with the ultraviolet illuminance targetvalue calculated by the arithmetic equations, the control unit beingresponsive to the comparison result showing that the ultravioletilluminance target value is higher, so that the control unit makes acontrol to increase an output of ultraviolet lamps in the firstultraviolet radiation device; and the control unit being responsive tothe comparison result showing that the ultraviolet illuminance targetvalue is lower, so that the control unit performs a control to decreasethe output of the ultraviolet lamps in the first ultraviolet radiationdevice.
 10. A water treatment system according to claim 2, furthercomprising: an ultraviolet illuminance meter to measure an ultravioletilluminance in the inside of the second ultraviolet radiation device,wherein the control unit has arithmetic equations set for calculating anultraviolet amount target value based on an ultraviolet radiationeffect, and an ultraviolet illuminance target value based on a flow ratemeasurement value and retention time of raw water and the ultravioletamount target value; and compares a measurement value of the ultravioletilluminance meter with the ultraviolet illuminance target valuecalculated by the arithmetic equations, the control unit beingresponsive to the comparison result showing that the ultravioletilluminance target value is higher, so that the control unit makes acontrol to increase an output of the ultraviolet lamps in the secondultraviolet radiation device; and the control unit being responsive tothe comparison result showing that the ultraviolet illuminance targetvalue is lower, so that the control unit makes a control to decrease theoutput of the ultraviolet lamps in the second ultraviolet radiationdevice.
 11. A water treatment system according to claim 1, furthercomprising: a raw water turbidity meter which measures a turbidity ofthe raw water at the front stage process; and a raw water fluorescenceanalyzer which measures a fluorescence intensity of the raw water,wherein the control unit controls an output of ultraviolet lamps in thefirst ultraviolet radiation device on the basis of the respectivemeasurement results of the raw water turbidity meter and the raw waterfluorescence analyzer.
 12. A water treatment system according to claim11, wherein the control unit calculates an ultraviolet transmittance ofthe raw water from the respective measurement results of the raw waterturbidity meter and the raw water fluorescence analyzer; and the controlunit is responsive to a calculation result showing a lower transmittancethan a preset reference value, so that the control unit makes a controlto stop the operation of the first ultraviolet radiation device, and tomake an output of ultraviolet lamps built in the second ultravioletradiation device higher than a standard value.
 13. A water treatmentsystem according to claim 12, further comprising: a bypass pipe whichconfigures a flow route that is not subject to the ultraviolet radiationof the first ultraviolet radiation device, wherein when the operation ofthe first ultraviolet radiation is stopped, the raw water is sent viathe bypass pipe to the rear stage process.
 14. A water treatment systemaccording to claim 13, further comprising: an ultraviolet illuminancemeter to measure an ultraviolet illuminance in the inside of the firstultraviolet radiation device, wherein the control unit has arithmeticequations set for calculating an ultraviolet amount target value basedon an ultraviolet radiation effect, and an ultraviolet illuminancetarget value based on a flow rate measurement value and retention timeof the raw water and the ultraviolet amount target value; and compares ameasurement value of the ultraviolet illuminance meter with theultraviolet illuminance target value calculated by the arithmeticequations, the control unit being responsive to a comparison resultshowing that the ultraviolet illuminance target value is higher, so thatthe control unit makes a control to increase an output of ultravioletlamps in the first ultraviolet radiation device; and the control unitbeing responsive to the comparison result showing that the ultravioletilluminance target value is lower, so that the control unit performs acontrol to decrease the output of the ultraviolet lamps in the firstultraviolet radiation device.
 15. A water treatment system according toclaim 13, further comprising: an ultraviolet illuminance meter tomeasure an ultraviolet illuminance in the inside of the secondultraviolet radiation device, wherein the control unit has arithmeticequations set for calculating an ultraviolet amount target value basedon an ultraviolet radiation effect, and an ultraviolet illuminancetarget value based on a flow rate measurement value and retention timeof the raw water and the ultraviolet amount target value; and compares ameasurement value of the ultraviolet illuminance meter with theultraviolet illuminance target value calculated by the arithmeticequations, the control unit being responsive to a comparison resultshowing that the ultraviolet illuminance target value is higher, so thatthe control unit makes a control to increase an output of ultravioletlamps in the second ultraviolet radiation device; and the control unitbeing responsive to the comparison result showing that the ultravioletilluminance target value is lower, so that the control unit makes acontrol to decrease the output of the ultraviolet lamps in the secondultraviolet radiation device.
 16. A water treatment system according toclaim 12, further comprising: an ultraviolet illuminance meter tomeasure an ultraviolet illuminance in the inside of the firstultraviolet radiation device, wherein the control unit has arithmeticequations set for calculating an ultraviolet amount target value basedon an ultraviolet radiation effect, and an ultraviolet illuminancetarget value based on a flow rate measurement value and retention timeof the raw water and the ultraviolet amount target value; and compares ameasurement value of the ultraviolet illuminance meter with theultraviolet illuminance target value calculated by the arithmeticequations, the control unit being responsive to a comparison resultshowing that the ultraviolet illuminance target value is higher, so thatthe control unit makes a control to increase an output of ultravioletlamps in the first ultraviolet radiation device; and the control unitbeing responsive to the comparison result showing that the ultravioletilluminance target value is lower, so that the control unit performs acontrol to decrease the output of the ultraviolet lamps in the firstultraviolet radiation device.
 17. A water treatment system according toclaim 12, further comprising: a second an ultraviolet illuminance meterto measure an ultraviolet illuminance in the inside of the secondultraviolet radiation device, wherein the control unit has arithmeticequations set for calculating an ultraviolet amount target value basedon an ultraviolet radiation effect, and an ultraviolet illuminancetarget value based on a flow rate measurement value and retention timeof the raw water and the ultraviolet amount target value; and compares ameasurement value of the second ultraviolet illuminance meter with theultraviolet illuminance target value calculated by the arithmeticequations, the control unit being responsive to when the a comparisonresult showing that the ultraviolet illuminance target value is higher,so that the control unit makes a control to increase an output ofultraviolet lamps in the second ultraviolet radiation device; and thecontrol unit being responsive to the comparison result showing that theultraviolet illuminance target value is lower, so that the control unitmakes a control to decrease the output of the ultraviolet lamps in thesecond ultraviolet radiation device.
 18. A water treatment systemaccording to claim 11, further comprising: an ultraviolet illuminancemeter to measure an ultraviolet illuminance in the inside of the firstultraviolet radiation device, wherein the control unit has arithmeticequations set for calculating an ultraviolet amount target value basedon an ultraviolet radiation effect, and an ultraviolet illuminancetarget value based on a flow rate measurement value and retention timeof the raw water and the ultraviolet amount target value; and compares ameasurement value of the ultraviolet illuminance meter with theultraviolet illuminance target value calculated by the arithmeticequations, the control unit being responsive to a comparison resultshowing that the ultraviolet illuminance target value is higher, so thatthe control unit makes a control to increase an output of ultravioletlamps in the first ultraviolet radiation device; and the control unitbeing responsive to the comparison result showing that the ultravioletilluminance target value is lower, so that the control unit performs acontrol to decrease the output of the ultraviolet lamps in the firstultraviolet radiation device.
 19. A water treatment system according toclaim 11, further comprising: an ultraviolet illuminance meter tomeasure an ultraviolet illuminance in the inside of the secondultraviolet radiation device, wherein the control unit has arithmeticequations set for calculating an ultraviolet amount target value basedon an ultraviolet radiation effect, and an ultraviolet illuminancetarget value based on a flow rate measurement value and retention timeof the raw water and the ultraviolet amount target value; and compares ameasurement value of the ultraviolet illuminance meter with theultraviolet illuminance target value calculated by the arithmeticequations, the control unit being responsive to a comparison resultshowing that the ultraviolet illuminance target value is higher, so thatthe control unit makes a control to increase an output of ultravioletlamps in the second ultraviolet radiation device; and the control unitbeing responsive to the comparison result showing that the ultravioletilluminance target value is lower, so that the control unit makes acontrol to decrease the output of the ultraviolet lamps in the secondultraviolet radiation device.
 20. A water treatment system according toclaim 1, further comprising: a sedimented water fluorescence analyzerwhich measures a fluorescence intensity of sedimented water at the rearstage process, wherein the control unit controls the output of theultraviolet lamps in the second ultraviolet radiation device on thebasis of a measurement result of the sedimented water fluorescenceanalyzer.
 21. A water treatment system according to claim 20, furthercomprising: an ultraviolet illuminance meter to measure an ultravioletilluminance in the inside of the first ultraviolet radiation device,wherein the control unit has arithmetic equations set for calculating anultraviolet amount target value based on an ultraviolet radiationeffect, and an ultraviolet illuminance target value based on a flow ratemeasurement value and retention time of the raw water and theultraviolet amount target value; and compares a measurement value of theultraviolet illuminance meter with the ultraviolet illuminance targetvalue calculated by the arithmetic equations, the control unit beingresponsive to a comparison result showing that the ultravioletilluminance target value is higher, so that the control unit makes acontrol to increase an output of ultraviolet lamps in the firstultraviolet radiation device; and the control unit being responsive tothe comparison result showing that the ultraviolet illuminance targetvalue is lower, so that the control unit performs a control to decreasethe output of the ultraviolet lamps in the first ultraviolet radiationdevice.
 22. A water treatment system according to claim 20, furthercomprising: an ultraviolet illuminance meter to measure an ultravioletilluminance in the inside of the second ultraviolet radiation device,wherein the control unit has arithmetic equations set for calculating anultraviolet amount target value based on an ultraviolet radiationeffect, and an ultraviolet illuminance target value based on a flow ratemeasurement value and retention time of the raw water and theultraviolet amount target value; and compares a measurement value of theultraviolet illuminance meter with the ultraviolet illuminance targetvalue calculated by the arithmetic equations, the control unit beingresponsive to a comparison result showing that the ultravioletilluminance target value is higher, so that the control unit makes acontrol to increase an output of ultraviolet lamps in the secondultraviolet radiation device; and the control unit being responsive tothe comparison result showing that the ultraviolet illuminance targetvalue is lower, so that the control unit makes a control to decrease theoutput of the ultraviolet lamps in the second ultraviolet radiationdevice.
 23. A water treatment system according to claim 1, furthercomprising: an ultraviolet illuminance meter to measure an ultravioletilluminance in the inside of the first ultraviolet radiation device,wherein the control unit has arithmetic equations set for calculating anultraviolet amount target value based on an ultraviolet radiationeffect, and an ultraviolet illuminance target value based on a flow ratemeasurement value and retention time of the raw water and theultraviolet amount target value; and compares a measurement value of theultraviolet illuminance meter with the ultraviolet illuminance targetvalue calculated by the arithmetic equations, the control unit beingresponsive to a comparison result showing that the ultravioletilluminance target value is higher, so that the control unit makes acontrol to increase an output of ultraviolet lamps in the firstultraviolet radiation device; and the control unit being responsive tothe comparison result showing that the ultraviolet illuminance targetvalue is lower, so that the control unit performs a control to decreasethe output of the ultraviolet lamps in the first ultraviolet radiationdevice.
 24. A water treatment system according to claim 1, furthercomprising: an ultraviolet illuminance meter to measure an ultravioletilluminance in the inside of the second ultraviolet radiation device,wherein the control unit has arithmetic equations set for calculating anultraviolet amount target value based on an ultraviolet radiationeffect, and an ultraviolet illuminance target value based on a flow ratemeasurement value and retention time of the raw water and theultraviolet amount target value; and compares a measurement value of theultraviolet illuminance meter with the ultraviolet illuminance targetvalue calculated by the arithmetic equations, the control unit beingresponsive to a comparison result showing that the ultravioletilluminance target value is higher, so that the control unit makes acontrol to increase an output of ultraviolet lamps in the secondultraviolet radiation device; and the control unit being responsive tothe comparison result showing that the ultraviolet illuminance targetvalue is lower, so that the control unit makes a control to decrease theoutput of the ultraviolet lamps in the second ultraviolet radiationdevice.
 25. A water treatment system according to claim 1, furthercomprising: an ultraviolet illuminance meter to measure an ultravioletilluminance in the inside of the first ultraviolet radiation device;ultraviolet lamp protective tubes which protect ultraviolet lamps builtin the first ultraviolet radiation device; and cleaning members whichclean surfaces of the ultraviolet lamp protective tubes, wherein thecontrol unit is responsive to the ultraviolet illuminance at thesurfaces of the ultraviolet lamp protective tubes measured by theultraviolet illuminance meter being out of an allowable range, so thatthe control unit makes a control to operate the cleaning members.
 26. Awater treatment system according to claim 25, wherein just after anactuation of the cleaning members, the control unit is responsive to theultraviolet illuminance at the surfaces of the ultraviolet lampprotective tubes measured by the ultraviolet illuminance meter being outof an allowable range, so that the control unit makes a control toprompt to exchange the ultraviolet lamps in the first ultravioletradiation device.
 27. A water treatment system according to claim 1,further comprising: an ultraviolet illuminance meter to measure anultraviolet illuminance in the inside of the second ultravioletradiation device; ultraviolet lamp protective tubes which protectultraviolet lamps built in the second ultraviolet radiation device; andcleaning members which clean surfaces of the ultraviolet lamp protectivetubes, wherein the control unit is responsive to the ultravioletilluminance at the surfaces of the ultraviolet lamp protective tubesmeasured by the ultraviolet illuminance meter being out of an allowablerange, so that the control unit makes a control to operate the cleaningmembers.
 28. A water treatment system according to claim 27, whereinjust after an actuation of the cleaning members, the control unit isresponsive to the ultraviolet illuminance at the surfaces of theultraviolet lamp protective tubes measured by the ultravioletilluminance meter being out of an allowable range, so that the controlunit makes a control to prompt to exchange the ultraviolet lamps in thesecond ultraviolet radiation device.
 29. A water treatment systemaccording to claim 1, further comprising: a bypass piping whichconfigures a flow route that is not subject to the ultraviolet radiationof the first ultraviolet radiation device, wherein when the operation ofthe first ultraviolet radiation is stopped, the raw water is sent viathe bypass pipe to the rear stage process.
 30. A water treatment systemaccording to claim 29, further comprising: an ultraviolet illuminancemeter to measure an ultraviolet illuminance in the inside of the firstultraviolet radiation device, wherein the control unit has arithmeticequations set for calculating an ultraviolet amount target value basedon an ultraviolet radiation effect, and an ultraviolet illuminancetarget value based on a flow rate measurement value and retention timeof the raw water and the ultraviolet amount target value; and compares ameasurement value of the ultraviolet illuminance meter with theultraviolet illuminance target value calculated by the arithmeticequations, the control unit being responsive to a comparison resultshowing that the ultraviolet illuminance target value is higher, so thatthe control unit makes a control to increase an output of ultravioletlamps in the first ultraviolet radiation device; and the control unitbeing responsive to when the comparison result showing that theultraviolet illuminance target value is lower, so that the control unitperforms a control to decrease the output of the ultraviolet lamps inthe first ultraviolet radiation device.
 31. A water treatment systemaccording to claim 29, further comprising: an ultraviolet illuminancemeter to measure an ultraviolet illuminance in the inside of the secondultraviolet radiation device, wherein the control unit has arithmeticequations set for calculating an ultraviolet amount target value basedon an ultraviolet radiation effect, and an ultraviolet illuminancetarget value based on a flow rate measurement value and retention timeof the raw water and the ultraviolet amount target value; and compares ameasurement value of the ultraviolet illuminance meter with theultraviolet illuminance target value calculated by the arithmeticequations, the control unit being responsive to a comparison resultshowing that the ultraviolet illuminance target value is higher, so thatthe control unit makes a control to increase an output of ultravioletlamps in the second ultraviolet radiation device; and the control unitbeing responsive to the comparison result showing that the ultravioletilluminance target value is lower, so that the control unit makes acontrol to decrease the output of the ultraviolet lamps in the secondultraviolet radiation device.